Work machines, such as crawler tractors, typically include a movement actuator or "joy stick". Some crawler tractors also include a return spring coupled to the joy stick which biases the joy stick in a neutral position (i.e. a position where the crawler tractor is prevented from being driven by the engine). The joy stick and return spring function to allow an operator to control the speed and direction of the crawler tractor while performing a work function. For example, when an operator of the crawler tractor applies a force to the joy stick such that the joy stick moves out of the neutral position to a forward drive position (i.e. the joy stick is moved toward the front end of the crawler tractor) the crawler tractor moves in a forward direction. When the operator stops applying force to the joy stick the return spring returns the joy stick to a neutral position so that the crawler tractor stops moving. In a similar manner, when the operator applies a force to the joy stick such that the joy stick moves out of the neutral position to a reverse drive position (i.e. the joy stick is moved toward the rear end of the crawler tractor) the crawler tractor moves in a rearward direction. As described above, when the operator stops applying force to the joy stick the return spring returns the joy stick to the neutral position so that the crawler tractor stops moving.
While the above described arrangement allows the operator to control the forward and rearward motion of the crawler tractor, it does have significant drawbacks. For example, if the crawler tractor is performing a work function such that the operator must hold the joy stick in the forward position for a long period of time (e.g. during a grading operation), the a arm of the operator can become fatigued as a result of having to constantly provide enough force to overcome the return spring bias.
In an attempt to address this problem some crawler tractors have joy sticks designed to remain in the forward or rearward position once placed there by the operator. However, a problem with this design is that the joy stick can be left in the forward or rearward position when the crawler tractor is turned off such that when it is restarted the joy stick is not located in the neutral position thereby causing damage to the components of the crawler tractor. Another problem with this design is that the previously described joy sticks (i.e. the joysticks designed to remain in the forward or rearward position) tend to require a large amount of force to move. Therefore, these joy sticks can also cause operator fatigue, particularly when used during the performance of a work function which requires the operator to change the direction of the crawler tractor a large number of times over a relatively short period of time (e.g. during a land clearing operation).
What is needed therefore is a control assembly for a work machine which overcomes the above-mentioned drawbacks.